For many years it has been recognized that one of the most critical elements of any vehicle suspension system is the shock absorber or damper which is coupled to the suspension system for the purpose of bringing a suspension system into equilibrium after deflection or extension responsive to road conditions or a maneuver by the vehicle. This is true whether the vehicle be a motorcycle, an off road vehicle, a conventional or performance vehicle or a racing automobile. The importance of the shock absorber is particularly recognized in the racing field where each race car has its own weight, distribution of that weight, power plant and handling characteristics. During the development of a race car, these may change and it would be desirable to change and experiment with the shock absorber characteristics to achieve optimum performance of the race car with each change in its design. It is further desirable for the race car to adjust it suspension system for different tracks or different conditions on each track. The difference between winning and a mediocre performance can often be traced to the shock absorbers.
Heretofore, shock absorbers have been made adjustable or changeable. The adjustments are typically of the compression and extension damping rates. Many of those require a partial disassembly of the shock absorber and a substitution of different elements such as orifices or internal adjustments. More recently, adjustable shock absorbers have been developed with exterior adjustments for both compression and rebound. Examples of such disclosures are found in the following United States Patents:
______________________________________ U.S. Pat. No. INVENTOR DATE ______________________________________ 3,256,960 M. Casimir June 21, 1966 3,351,160 de Koning et al Nov. 7, 1974 3,848,710 J. T. Thompson Nov. 19, 1974 3,960,251 A. J. Gorissen June 1, 1976 4,036,335 Thompson et al July 19, 1977 4,298,102 Nishikawa et al Nov. 3, 1981 4,305,486 A. A. Cowan Dec. 15, 1981 4,535,877 A. Shimokura Aug. 20. 1985 4,546,959 S. Tanno Oct. 15, 1985 4,635,906 S. Buma Jan. 13, 1987 4,741,416 F. Tanigawa May 3, 1988 4,744,444 C. L. Gillingham May 17, 1988 ______________________________________
and the following foreign patents:
______________________________________ COUNTRY NUMBER DATE ______________________________________ France 2,418,390 Sept. 21, 1979 ______________________________________
Further refinements of adjustable shock absorbers include those which are digitally or computer controlled and electrically operated such as the shock absorber disclosed in United States Patents:
______________________________________ 4,596,320 Shimokura et al June 24, 1986 4,664,409 Nakashima et al May 12, 1987 ______________________________________
Another critical factor in the design and operation of shock absorbers lies in the need for temperature compensation to avoid any dramatic or unpredictable change in characteristics resulting not from intentional adjustment or change in road conditions but due to temperature changes. These changes include ambient temperature change from early morning to the heat of the day, shock absorber temperature change from operation, change in viscosity of the oil medium contained within the shock absorber, change in density of the gas medium, change in dimensions of component parts of the shock absorber to name the most significant temperature changes. The results of such changes in temperature must be recognized in the design phase of the development of a shock absorber and must be counteracted by temperature sensitive elements within the shock absorber to compensate and hopefully eliminate any net change in operating characteristics of the shock absorber due to any of the foregoing uncontrollable temperature changes. Various attempts have been made in the past to provide temperature compensation in shock absorbers. These are disclosed in the following United states patents:
______________________________________ 3,088,555 W. A. Karlgaard May 7, 1963 3,944,197 A. Dachicourt Mar. 16, 1976 ______________________________________
Despite the development of shock absorbers over the many years, a number of problems continue to plague the field. They include:
1. Adjusting mechanisms tend to be complex and unreliable. PA1 2. The multiple adjusting mechanisms seldom, if ever, provide independence of each of the adjustments. PA1 3. Few of the adjustment mechanisms allow rapid adjustment without tools. PA1 4. High speed and low speed independent adjustments have not been achieved. PA1 5. Dual temperature compensation, one reflecting and compensating for the temperature change effect upon compression damping rate and a second one for rebound rate temperature effects have been lacking.